The objective of this proposal is to synthesize and evaluate novel, carbon-based nanostructure photosensitizers (PS) for the topical treatment of a variety of non-melanoma, pre-malignant and malignant cutaneous lesions, inflammatory dermatoses, and localized bacterial and fungal infections by topical photodynamic therapy (PDT). Our concept is based on a recently discovered family of molecules that have shown a remarkable ability to sensitize singlet oxygen under a variety of conditions. The visible light-absorbing photosensitizer has been shown in previous work to exhibit no dark toxicity. It has also been shown by our preliminary in vitro work to be internalized into a murine cancer cell line and a gram-positive bacterium where significant phototoxicity was observed upon irradiation. It is easily "tailored" by the methods of organic synthesis, which has the potential of leading to a combinatorial library of PS for different applications. After topical application of the PS to the affected area followed by a period of incubation, the area is selectively irradiated with light of appropriate wavelength and intensity. This causes the formation of reactive oxygen species (ROS) by the catalytic action of the nanostructure PS on molecular oxygen. The ROS cause a loss of viability in the affected cells.